Polymer Thin Film–Induced Tumor Spheroids Acquire Cancer Stem Cell–like Properties

Choi, Minsuk,Yu, Seung J.,Choi, Yoonjung,Lee, Hak R.,Lee, Eunbeol,Lee, Eunjung,Lee, Yumi,Song, Junhyuk,Son, Jin G.,Lee, Tae G.,Kim, Jin Y.,Kang, Sukmo,Baek, Jieung,Lee, Daeyoup,Im, Sung G.,Jon, Sangyo American Association for Cancer Research 2018 Cancer Research Vol.78 No.24

<P>A new cell culture technology enables highly tumorigenic 3D spheroids to be easily generated from various cancer cell sources in the common laboratory.</P><P><B></B></P><P>Although cancer stem cells (CSC) are thought to be responsible for tumor recurrence and resistance to chemotherapy, CSC-related research and drug development have been hampered by the limited supply of diverse, patient-derived CSC. Here, we present a functional polymer thin film (PTF) platform that promotes conversion of cancer cells to highly tumorigenic three-dimensional (3D) spheroids without the use of biochemical or genetic manipulations. Culturing various human cancer cells on the specific PTF, poly(2,4,6,8-tetravinyl-2,4,6,8-tetramethyl cyclotetrasiloxane) (pV4D4), gave rise to numerous multicellular tumor spheroids within 24 hours with high efficiency and reproducibility. Cancer cells in the resulting spheroids showed a significant increase in the expression of CSC-associated genes and acquired increased drug resistance compared with two-dimensional monolayer-cultured controls. These spheroids also exhibited enhanced xenograft tumor-forming ability and metastatic capacity in nude mice. By enabling the generation of tumorigenic spheroids from diverse cancer cells, the surface platform described here harbors the potential to contribute to CSC-related basic research and drug development.</P><P><B>Significance:</B></P><P>A new cell culture technology enables highly tumorigenic 3D spheroids to be easily generated from various cancer cell sources in the common laboratory.</P>

Characteristics of Tropical Cyclone Battering the Korean Peninsula

Yumi Choi,Sung-Hun Kim,MinHo Kwon,Daehyun Kang 한국기상학회 2023 한국기상학회 학술대회 논문집 Vol.2023 No.11

Subtropical North Pacific Modes Modulating Strong El Niño’s Impact on Western North Pacific Tropical Cyclone Genesis during the Subsequent Summer

Yumi Choi,MinHo Kwon,Kyung-Ja Ha 한국기상학회 2019 한국기상학회 학술대회 논문집 Vol.2019 No.10

Phonological Awareness in Terms of Stimulus Presentation and Syllable Position in Children with Speech Sound Disorders and Typically Developing Children

Yumi Choi(최유미),Seunghee Ha(하승희) 한국언어청각임상학회 2018 Communication Sciences and Disorders Vol.23 No.2

Objectives: This study aims to compare the performance of phonological awareness tasks according to stimuli presentation methods and syllable positions in children with speech sound disorders (SSD) and typically developing children. Methods: Sixteen children with SSD and 16 typically developing children participated in the study. Three-syllable words were presented using auditory and visual stimuli and the children were asked to identify the first and final syllable in each word. For the auditory stimuli, each test word was presented only with oral speech. For the visual stimuli, each test word was presented as a picture, and children were asked to choose appropriate pictures for the task. Results: The results indicated that children with SSD showed significantly lower performances than typically developing children. When tasks were presented visually, both groups showed significantly higher phonological awareness skills in the visual stimuli condition than the auditory stimuli condition. Also, both groups showed significantly higher phonological awareness skills in first syllable identification than final syllable identification. There was also a significant interaction between stimuli presentation methods and syllable positions. Conclusion: This study suggests that children with SSD may have limitations in phonological awareness skills, which can be different depending on the methods of stimulus presentation and syllable position of the tasks. The comparison of performances between visual and auditory stimulus tasks will help identify where children may show weaknesses and vulnerabilities in the speech production process. This study suggests that evaluation and intervention on phonological awareness skills are needed for children with SSD. 배경 및 목적: 본 연구는 첫 음절과 끝 음절 확인 음운인식 과제를 통해 자극제시 방법 및 반응방법과 음절 위치에 따라 말소리장애와 일반아동 간에 수행력에 차이가 있는지 살펴봄으로써 음운인식 과제 수행을 위해서 일반적으로 필요한 기저능력에 대해서 논의하고자 하였다. 방법: 만 4-6세의 말소리장애 아동 16명과 일반아동 16명이 연구에 참여하였다. 3음절 의미 단어의 첫 음절과 끝 음절 확인 과제를 청각적, 시각적 자극으로 각각 제시하였다. 청각적 자극제시 및 반응은 검사자가 말로 과제를 제시하면 아동이 말로 반응하였고, 시각적 자극제시 및 반응은 검사어를 그림으로만 제시하고, 해당 그림을 아동이 지적하였다. 결과: 말소리장애 아동의 음운인식 수행력이 일반아동보다 유의미하게 낮은 것으로 나타났다. 두 집단 모두 과제를 청각적 자극으로 제시하는 것보다 시각적 자극으로 제시하였을 때 음운인식 수행력이 유의미하게 높았고, 끝 음절 확인 과제보다 첫 음절 확인 과제의 수행력이 유의미하게 높았다. 논의 및 결론: 본 연구결과는 말소리장애 유무와 자극제시 및 반응 유형, 음절 위치에 따라 음운인식 능력이 달라질 수 있음을 보여준다. 자극제시 방법에 따른 음운인식 능력을 비교하는 것은 말처리 과정에서 어느 단계에 취약성을 보이는지 객관적으로 확인하는 데 도움이 될 것이다.

The Fundamental Planes of E+A galaxies and GALEX UV-excess early-type galaxies: revealing their intimate connection

Choi, Yumi,Goto, Tomotsugu,Yoon, Suk-Jin Blackwell Publishing Ltd 2009 Monthly notices of the Royal Astronomical Society Vol.395 No.2

<P>ABSTRACT</P><P>Strong Balmer absorption lines and the lack of Hα and [O <SMALL>II</SMALL>] emission lines signify that E+A galaxies are post-starburst systems. Recent studies suggest that E+As may undergo the transition from the ‘blue cloud’ to the ‘red sequence’ and eventually migrate to red-sequence early-type galaxies. An observational validation of this scenario is to identify the intervening galaxy population between E+As and the red sequence. Motivated by recent findings with Galaxy Evolution Explorer (GALEX) that an unexpectedly large fraction of early-type galaxies exhibit ultraviolet (UV) excess (i.e. blue UV – optical colours) as a sign of recent star formation (RSF), we investigate the possible connection of the UV-excess galaxies to E+As. In particular, we examine the Fundamental Plane (FP) scaling relations of the currently largest sample of ∼1000 E+As selected from the Sloan Digital Sky Survey (SDSS) and ∼20 000 morphologically selected SDSS early-type galaxies with GALEX UV data. The FP parameters, combined with stellar population indicators, reveal a certain group of UV-excess early types that bridge between E+As and quiescent red galaxies. The newly identified galaxies are the post-starburst systems characterized by UV-excess but no Hα emission. This is essentially a conceptual generalization of ‘E+A’, in that the Balmer absorption line in the ‘E+A’ definition is replaced with UV – optical colours that are far more sensitive to RSF than the Balmer lines. We refer to these UV-excess galaxies as ‘E+a’ galaxies (named after ‘E+A’), which stand for elliptical (‘E’) galaxies with a minority of A-type (‘a’) young stars. The species are either (1) galaxies that experienced starbursts weaker than those observed in E+As (1 ∼ 10 per cent of E+As, ‘mild E+As’) or (2) the products of passively evolved E+As after quenching star formation quite a while ago (∼1 Gyr, ‘old E+As’). We suggest that the latter type of E+a galaxies (i.e. old ‘E+As’) represents the most recent arrival to the red sequence in the final phase of the E+A to red early-type transition.</P>

Comparisons Between Normocalcemic Primary Hyperparathyroidism and Typical Primary Hyperparathyroidism

Choi Hye Ryeon,Choi Sun Hyung,Hong Namki,Rhee Yumie,Kim Jin Kyong,Lee Cho Rok,Kang Sang-Wook,Lee Jandee,Jeong Jong Ju,Nam Kee-Hyun,Chung Woong Youn 대한의학회 2022 Journal of Korean medical science Vol.37 No.13

Background: Normocalcemic primary hyperparathyroidism (NPHPT) was first described in 2008. It is defined as consistently elevated serum parathyroid hormone (PTH) levels with normal serum calcium (sCa) concentration, after excluding secondary causes of PTH elevation. However, the exact definition and management strategy for NPHPT remain controversial. We retrospectively investigated the clinicopathological features and short-term outcomes of NPHPT patients. Methods: A total of 280 patients who were surgically indicated for primary hyperparathyroidism (PHPT) at the Yonsei Severance Medical Center between 2015 and 2019 were included. Patients were classified according to preoperative PTH, corrected sCa, and ionized calcium (iCa) levels as follows: typical primary hyperparathyroidism (TPHPT, elevated PTH, sCa, and iCa, n = 158) and NPHPT (elevated PTH, normal sCa, n = 122). Results: NPHPT was commonly seen in younger individuals (aged < 50 years, P = 0.025); nephrolithiasis and bone fractures were common. Preoperative PTH level was higher in the TPHPT group (P < 0.001). The NPHPT group had higher numbers of multiple parathyroid lesions (P = 0.004) that were smaller (P = 0.011). NPHPT patients were further divided into two subgroups according to iCa levels: the elevated (n = 95) and normal iCa (n = 27) groups. There was no significant difference between the two subgroups regarding symptoms and multiplicity of lesions. Conclusion: We found that NPHPT may be a heterogeneous disease entity of PHPT with high rates of multi-gland disease, which appears to be biochemically milder but symptomatic. Intraoperative PTH monitoring might help increase the surgery success rate. Moreover, the short-term outcomes of NPHPT after surgery did not differ from that of TPHPT.

Hole Expansion Characteristics of W-Tempered 7075 Aluminum Alloy Sheet in Comparison with Peak Aged T6 Tempered Alloy Sheet

Yumi Choi,Jinwoo Lee,Hyuk Jong Bong,Myoung-Gyu Lee 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1

The hole expansion formability of W-tempered aluminum 7075 sheet, which is prepared by solution heat treatment and rapid cooling, is investigated comparatively with the peak aged T6 tempered alloy. The W temper heat treatment has been known to be a potential application to cold forming of high strength aluminum including 7075 alloy as an alternative to the warm or hot forming process. The hole expansion tests are designed with a conical punch and the holes are fabricated using wire-cut and punching. Basic mechanical properties and microstructure analyses are performed to study the effect of the strength and ductility in tension on the hole expansion ratios of specimens with different tempers and hole conditions. From the experimental study, the following conclusions are mainly reached. (1) The W-tempered sheets show much improved HER than T6 tempered sheets; i.e., 31 (T6) vs. 58% (W) for wire-cut hole and 19 (T6) vs. 57% (W) for punched hole. (2) The HER of W-tempered sheets show very similar HER values between wire-cut and punched hole specimens, which has not been commonly reported. (3) The initiation of cracks at hole edges is different depending on hole preparation; i.e., RD or TD (wire-cut T6 and wire-cut and punched W) vs. RD, DD, and TD (punched T6). (4) The KAM map validates the cause of lower HER of punched specimen attributes to earlier crack initiation by prior plastic deformation during punching, but the strengthening of shear affected zone has limited effect on HER. (5) The HERs of T6 and W tempered sheets are well correlated to the yield strength, ultimate tensile strength, and total elongation. However, the effect of post uniform elongation on HER is not correlated to the existing report.

The Fundamental Planes of "E+A" Galaxies and GALEX UV-excess Early-typeGalaxies: Revealing their Evolutionary Connection

Yumi Choi,Tomotsugu Goto,Suk-Jin Yoon 한국천문학회 2008 天文學會報 Vol.33 No.1

Subseasonal shift in tropical cyclone genesis over the western North Pacific in 2013

Choi, Yumi,Ha, Kyung-Ja Springer-Verlag 2018 Climate dynamics Vol.51 No.11

Impact of Discrepancy in Atmospheric Soundings between Reanalysis and Radiosonde Data on Tropical Cyclone Potential Intensity over the western North Pacific

Yumi Choi,MinHo Kwon,Sang-Wook Yeh,Kang-Jin Lee,JaeHak Lee,Sok Kuh Kang,Yoon Chil Kim,Bonhwa Ku,Sung-Hun Kim 한국기상학회 2022 한국기상학회 학술대회 논문집 Vol.2022 No.10